1. Field of the Invention
The present invention relates to a method for pretreating cellulosic biomass by using a mixture catalyst of an acid and a base in pretreatment for pretreatment, saccharification, and fermentation of lignocellulose in just one reactor (one-pot process).
2. Discussion of Related Art
In order to produce a biofuel from lignocellulose, recalcitrance of lignocellulose itself should be alleviated through suitable physicochemical pretreatment. However, since a major pretreatment process is performed at a high temperature and a pH in a range of a strong acid or a strong base, degradative products (furfural, etc.) are generated, which cause not only sugar loss but also the inhibition of a yeast fermentation process.
Meanwhile, a process for producing a biofuel from lignocellulose mainly progresses through pretreatment, solid/liquid separation, solids washing, liquid detoxification, liquid neutralization, enzymatic hydrolysis, and ethanol fermentation processes. Among these, unit processes for removal of inhibitory compounds such as solid/liquid separation, solids washing, liquid detoxification, and liquid neutralization make total operating costs significantly increase. Therefore, there are needs for the development of a strain which is tolerable to the inhibitor, or of a new process in which an inhibitor is not produced.
As part of such efforts, consolidate bioprocessing (CBP) in which enzyme production and fermentation are performed in a single step using a genetically modified microorganism was suggested (Lynd et at., Biotechnol. Prog., 1999, 15, pp. 777-793), but has not realized yet. Also, whole slurry fermentation in which saccharification and fermentation are performed without a solid/liquid separation process was suggested (Jung et at., Bioresour. Technol., 2013, 132, pp. 109-114), but was again found inconvenient to additionally remove inhibitors using activated carbon, etc. In addition, a method for combining pretreatment with hydrolysis using an ionic liquid was suggested as well, but was found inconvenient in that an ionic liquid should be separated and recovered after pretreatment due to costs and toxicity thereof, and as part of some other integrated process, a simultaneous saccharification and fermentation process itself is impossible (Shi et al., Green Chem., 2013, 15, pp. 2579-2589).
Therefore, the development of processing technology capable of simplifying the overall process, reducing total operating costs, and improving the production yield of ethanol is being demanded.